It is the object of this invention to provide complete combustion under conditions which minimize the formation of pollutants, including oxides of nitrogen, carbon monoxide and partially burned hydrocarbons.
In substantially all present-day internal combustion engines with spark ignition, a near rich fuel-air mixture is utilized to give reliable ignition and combustion for rapid engine acceleration and smooth operation. Additional air may be introduced into the exhaust system to complete the combustion process. Also, exhaust products are sometimes introduced into the air intake system to reduce the concentration of oxygen and thereby reduce the formation of oxides of nitrogen by reducing the combustion temperature.
Although these techniques are effective in reducing the pollutants produced by an engine, the additional equipment and reduction of power from a given size engine make these techniques relatively unattractive.
In the invention disclosed herein, these shortcomings have been eliminated for four-stroke and two-stroke cycle engines. This invention provides a means for reliably igniting a quite lean mixture in the primary or main cylinder. A small auxiliary cylinder with spark ignition has a near rich mixture which is reliably ignited by the spark under all operating conditions. The energy released and the turbulence created when the hot gases from the auxiliary cylinder flow into the main cylinder cause ignition over a wide operating range mixture strength. Thus, relatively cool and complete combustion takes place in the main cylinder which results in lower concentrations of unburned hydrocarbons, carbon monoxide and oxides of nitrogen in the engine exhaust.
The hot gases from the small auxiliary cylinder mix with the products of combustion in the main cylinder early in the expansion cycle thereby forming an overall lean products of combustion. The small piston in the auxiliary cylinder aids in the mixing process by expelling the burning gases into the main cylinder.
In addition to the clean burning characteristics of this form of internal combustion engine, the control of the engine is not substantially more difficult than the control for conventional engines. The small auxiliary cylinder may be operated with full atmospheric intake pressure at all times while the main cylinder can be controlled by conventional inlet throttling. Thus, only conventional control means are required.
In accomplishing these and other objects, I have provided details of structure, exemplary forms of which are illustrated in the accompanying drawings herein.